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https://doi.org/10.5194/bg-2020-3
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-3
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 12 Feb 2020

Submitted as: research article | 12 Feb 2020

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This preprint is currently under review for the journal BG.

Denitrification, carbon and nitrogen emissions over the Amazonian wetlands

Jérémy Guilhen1,2, Ahmad Al Bitar2, Sabine Sauvage1, Marie Parrens2,3, Jean-Michel Martinez4, Gwenael Abril5,6, Patricia Moreira-Turcq7, and José-Miguel Sanchez-Pérez1 Jérémy Guilhen et al.
  • 1Laboratoire Ecologie Fonctionnelle et Environnement (EcoLab), Institut national polytechnique de Toulouse (INPT), CNRS, Université de Toulouse (UPS), France
  • 2Centre d’Observation de la Bioshpère (CESBIO), CNES, Université de Toulouse (UPS), France
  • 3Dynafor, Université de Toulouse, INRAE, INPT, INP-PURPAN, Castanet-Tolosan, France
  • 4Géosciences Environnement Toulouse (GET), IRD/CNRS, Université Toulouse (UPS), France
  • 5Biologie des Organismes et Ecosystèmes Aquatiques (BOREA), Muséum National d’Histoire Naturelle, Paris, France
  • 6Programa de Geoquímica, Universidade Federal Fluminense, Outeiro São João Batista, Niterói, RJ, Brazil
  • 7IRD (Institut de Recherche pour le Développement), GET (Géosciences Environnement Toulouse), UMR 5563, Lima, Peru

Abstract. In this paper, we quantify CO2 and N2O emissions from denitrification over the Amazonian wetlands. The study concerns the entire Amazonian wetland ecosystem with a specific focus on three focal locations: the Branco Floodplain, the Madeira Floodplain and the floodplains alongside the Amazon River. We adapted a simple denitrification model to the case of tropical wetlands and forced it by open water surface extent products from the Soil Moisture and Ocean Salinity (SMOS) satellite. A priori model parameters were provided by in situ observations and gauging stations from the HyBAm observatory. Our results show that the denitrification and emissions present a strong cyclic pattern linked to the inundation processes that can be divided into three distinct phases: activation – stabilization – deactivation. We quantify the average yearly denitrification and associated emissions of CO2 and N2O over the entire watershed at 17.8 kgN/ha/yr, 0.37 gC/m2/yr and 0.18 gN/m2/yr respectively. When compared to local observations, it was found that the CO2 emissions accounted for 0.01 % of the integrated ecosystem, which emphasis the fact that minor changes to the land cover may induce strong impacts to the Amazonian carbon budget. Our results are quite consistent with the state of the art global nitrogen models with a positive bias of 28 %. When compared to other wetlands in different pedo-climatic environments we found that the Amazonian wetlands have close emissions of N2O to the tropical Congo wetlands and lower emissions than the tropical and temperate anthropogenic wetlands of the Garonne river, the Rhine river, and south-eastern Asia rice paddies. In summary our paper shows that a data driven approach can be successfully applied to quantify N2O and CO2 fluxes associated with denitrification over the Amazon basin. In the future, the use of higher resolution remote sensing product from sensor fusion or new sensors like the SWOT mission will permit the transposition to other large scale watersheds in tropical environment.

Jérémy Guilhen et al.

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Jérémy Guilhen et al.

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Short summary
The amount of greenhouse gases released to the atmosphere by human industries and agriculture, such as carbon dioxide (CO2) and nitrous oxide (N2O), has been constantly increasing for the last decades. The main objective was to develop a methodology which makes consistent both satellite observations and modelling of the Amazon basin to identify and quantify the role of wetlands to GES emissions. We showed that these areas produce non negligeable emissions and are linked to landuse cover.
The amount of greenhouse gases released to the atmosphere by human industries and agriculture,...
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